Explosive composition for detonating rivets



Patented Nov. 4, 1941 EXPLOSIVE COMPOSITION FOR DETONATING RIVETS Edmundvon Herz, C'ologne-Dellbruck, Heinz Gawlick, Furth, Bavaria, and HansRathsburg, Stadeln uber Nuremberg, Germany, assignors, by mesneassignments, to E. I. 'du Pont de Nemours & 00., a corporation ofDelaware No Drawing. Application June 3, 1939, Serial No. 277,322. InGermany July 16, 1938 14 Claims. (01. "52-4) As a charge for detonatingrivets, the ignition of which -is brought about by indirect or directheating of the rivet .to' the explosion temperature of the chargedexplosive, it has been proposed to use heavy metal azides the highexplosion point of ,which is reduced to about 150 by addition ofexplosives which explode at low temperature.

Mixtures of lead azide and guanyl-nitrosaminoguanyltetrazene, brieflyreferred to as tetrazene, are particularly eificient and readilyprepared preparations in accordance with this proposal.

In view of the fact that the, deposit of metallic lead arising in thedetonation of lead azide leads in the case of light metal rivetings tohigh electro-corrosion, detonating charges which are poor. in lead azideand the lead azide content of which amounts only to about 18-20%, havealready been prepared. The lead azide portion which is omitted isin'this case replaced by a mixture of highly shattering nitro-bodies oresters and inert diluents.

Still more suitable, however, were compositions of metal-free initialexplosives or of explosives which contain the same metal as that ofwhich the material to be riveted consists. Unfortunately, the knownpurely organic initial explosives are quite out of the questionfor thislargescale use, since they are far toosensitive and partly also are notstable to'storage, for example, nitrodiazobenzene perchlorate andcyanuric triazide.

It has now been found that mixtures of mannite hexanitrateand'tetrazen'e on rapid heating detonate with a high starting velocity(i. e. a

high velocity of the chemical action leading to.

- If, on the other hand, the mannite hexanitrate is mixed with about 30%tetrazene, then on heating in the rivet this mixture detonates' with thehigh starting velocity'peculiar to initial explosives and with highshattering power. Peculiarly enough, this action occurs only onuniformly heating the whole quantity of explosive in the rivet and notwith flame and spark ignition, which at best leads only to a burningaway of this explosive mixture. This property is very remarkable and isfundamentally important from a technical point of view, since thiscomposition affords a great degree of safety from accidental explosions,both in the case of the loose composition as well as in the'case of thefinally charged rivets.

The mixture in question, at highcharging densities, i. e. when pressedunder high pressure,

possesses such a brisance that it may be used only for verystrong-walled rivets. In the rivets ordinarily used, having relativelythin Wall strength of the explosive chamber, the charging density shouldnot exceed about 1, on account of the danger of complete destruction ofthe rivet. Lo'w charging densities, moreover, mean a charge pressed onlyslightly, which, as the result of its lack of compactness, tends tobecome detached and to crumble out; therefore the safety intransportation and use of such explosive rivets is greatly impaired.Such a lightly pressed charge of low charging density, therefore, makesa special covering of the rivet opening by a strong layer of lacquer, orthe like,'necessary. Since such measures make the manufacture expensive,it is more expedient to dilute the explosive charge so greatly by theaddition of inert materials and to diminish its energy to such an extentthereby that even high charging densities'oannot lead to an excessive,destructive brisance. In such explosive rivets, with charges of highloading density, the explosive charge is so strongly pressed thatloosening and falling out, even without a protective covering, isentirely outof the question. This dilution, however, cannot be efiectedas when using pronounced initial explosives, with any desiredpulverulent substances, e. g. kieselguhr, since such substances, even inthe smallest quantity, prevent the development of detonation.

On the other hand, it has been found surprisingly enough that thisnecessary dilution is to be carried out more particularly with metalpowders and with powdered substances of good thermal conductivity, suchas, for example, metal carbides, silicides, sulphites, oxides, etc. Thedetonation sensitivity of the mannite hexanitratetetrazene mixture isnot only in no way hindered by this addition but,quite on the contrary,is enhanced to a considerable extent, apparent from the great uniformityof, the expansion or splaying results. It is certainly remarkable thatthe proportion of diluent can, in the case of satisfactorily conductingmetal powders, e. g. silver, copper and aluminium powder, be raised upto about of the mixture, without the detonation sensitivity and the highstarting velocity being eral, initiated at one end and does not travellayerwise through-the explosive charge but takes place practically atthe same moment at all points of the charge, there is an increase in the"starting" velocity and a shortening in the time of detonation. Thebraking eiTect of large quantities of inert substance is completelycompensated for by this new eflect and the action of the detonation ismade still more uniform by the increased decomposition velocity.

,In the case of rivetings of metal pieces which are sensitive tocorrosion, the diluent must be so chosen that the explosion residues canin no circumstances lead to an electrical difference in voltage wtih themetal coated therewith, since the current fiow set up under the actionof moisture may lead to severe corrosion. Asdilut-' ing agent,therefore, for the most part always the metal powder or the metalcompound which corresponds to the rivet metal, or to the metal beingriveted, will be employed. In the case of rivetings of light metals, e.g. in aircraft construction, aluminium powder will exclusively be used.

. Example of a mixture for light metal rivets The mannite hexanitratemay also be replaced by the nitrates of tetrabasic and pentabasicalcohols, e. g. by erythrite tetranitrate.

A particular advantage of these explosive compositions is theinsensitivity towards mechanical influences brought about by the largequantity of metal powder which makes the charging and pressing of therivets filled therewith practically free from danger, I

-These mixtures containing metal powder also areignited by flame onlywith very great difilculty and then they burn away harmlessly. I

The present invention therefore represents a noteworthy advance over thepure initial compositions sensitive to flame, impact and frictionheretofore proposed and used.

We claim:

1. In an explosion rivet an explosive charge comprising a nitrate of asolid polyvalent alcohol containing between 4 and 6 hydroxy groups, andguanylmitrosamino guanyl-tetrazene.

2. In an explosion rivet an explosive charge comprising a nitrate of atetravalent alcohol, and guanyl-nitrosamino guanyl-tetrazene.

3. In an explosion rivet an explosive charge comprising the nitrate of apentavalent alcohol, and guanyl-nitrosamino guanyl-tetrazene.

4. In an explosion rivet an explosive charge comprising the nitrate of ahexavalent alcohol, and guanyl-nitrosamino 'guanyl-tetrazene.

5. In an explosion rivet an explosive charge comprising mannitehexanitrate, and guanyl-nitrosamino guanyl-tetrazene.

6. In an explosion rivet an explosive charge comprising the nitrate of asolid polyvalent alcohol, guanyl-nitrosamino guanyl-tetrazene, and apowder substance of good thermal conductivity selected from the classconsisting of metals, metal carbides, metal sulfides, metal sulfites,and metal oxides.

7. In an explosion .rivet an explosive chargecomprisingmannitehexanitrate,guanyl-nitrosamino guanyl-tetrazene, and apowder substance of good thermal conductivity selected from the classconsisting of metals, metal carbides, metal sulfides, metal sulfites,and metal oxides.

8. In an explosion rivet an explosive charge comprising mannitehexanitrate, guanyl-nitrosamino guanyl-tetrazene, and a metal powder.

9. In an explosion rivet an explosive charge comprising mannitehexanitrate, guanyl-nitrosamino guanyl-tetrazene; and aluminum powder.

10. In an explosion rivet an explosive charge comprising a nitrate ofapolyhydroxy alcohol containing between 4 and 6 hydroxy groups a finelydivided diluent of high thermal conductivity selected from the classconsisting of metals, metal carbides, metal sulfides, metal sulfites,and metal oxides, and tetrazene.

11. In an explosion rivet an explosive charge comprising a. nitrate of apolyhydroxy alcohol containing between 4 and 6 hydroxy groups,tetrazene, and a finely divided metal.

12. In an explosion rivet an explosive charge comprising a nitrate of apolyhydroxy alcohol containing between 4 and 6 hydroxy'groups,tetrazene, and finely divided silver. I

13. In an explosionrivet an explosive charge comprising a nitrate of apolyhydroxy alcohol containing between 4 and 6 hydroxy groups,tetrazene, and finely divided copper.

14. In an explosion rivet an explosive charge eomprisinga nitrate of apolyhydroxy alcohol containing between 4 and 6 hydroxy groups,tetrazene, and finely divided aluminum.

\ EDMUND VON HERZ.

HEINZ GAWLICK. HANS RATHSBURG.

